1. Field of the Invention
The present invention relates generally to apparatus and methods for the recanalization of stenosed arteries. More particularly, the invention relates to the use of laser catheters for the ablation of artherosclerotic plaque and thrombus.
Laser angioplasty relies on the use of optical fiber catheters to direct laser energy at arterial obstructions, such as plaque and thrombus. The technique has been used to remove obstructions from peripheral and coronary arteries. The catheters function by directing laser energy in a narrow, focused beam of light, typically having diameter of about 100-200 .mu.m. The incident laser radiation heats and vaporizes the plaque, generally producing soluble by-products which are removed safely by the blood. The effect of the laser radiation, however, is generally limited to a path having in diameter approximately equal to that of the laser beam. Thus, sufficient opening of the obstructed region of the artery is not always achieved.
It would therefore be desirable to provide apparatus and methods for using lasers to open relatively wide channels through arterial obstructions. In particular, it would be desirable to provide laser catheters capable of sweeping laser beam(s) across an arterial obstruction to ablate a relatively wide area.
2. Description of Prior Art
Livesay et al. (1985) Herz 10: 343-350 and Macruz et al. (1985) Lasers in Surgery and Medicine 5: 199-218 are review articles describing the state of the art in laser angioplasty. Ginsburg et al. (1984) Clin. Cardiol. 7: 54-58 and Ginsburg et al. (1985) Radiology 156: 619-624 describe case studies where laser angioplasty has been used to open stenosed regions in the peripheral arteries. Takekawa et al. (1985), Nippon Acta Radiologica 45: 1167-1169 describes the combination of laser angioplasty and balloon angioplasty for opening stenosed regions of the iliac and femoral arteries. U.S. Pat. No. 4,418,688 describes a laser catheter employing a cable system for adjusting the alignment of the catheter tip.